Technical Field
The present invention relates to a method for producing a stator by disposing an insulator with a coil around each tooth of a stator and integrally sealing the stator and the coil with a sealing resin body.
Background Art
In order to reduce noise of motors, a method has been applied that disposes an insulator with a coil around each tooth of a stator core, and molds resin around the tooth and the coil to integrally seal them with a sealing resin body.
In molding of such a sealing resin body, it is concerned that when a stator core, which has an insulator with a coil disposed around its tooth, is placed in a die and resin is injected into the die, the coil or the insulator may move or deform due to the pressure of the resin. Such a problem is prominent not in the method of forming a coil by directly winding a winding wire around a tooth but in the method of disposing a coil, which is obtained by winding a winding wire in advance, around a tooth with an insulator (or insulating paper) interposed therebetween.
Herein, the conventional method for producing a stator (Embodiment 1 of the conventional production method) will be described with reference to FIGS. 5 to 7. Although FIG. 5 illustrates only a part of a stator core, the stator core practically has a plurality of teeth that are disposed in circumferential direction and extend radially. In the method shown in FIG. 5, an insulator with a coil is loosely fit around each tooth and is placed in a die.
In the method shown in FIG. 5, insulation between the coil and each tooth is achieved using an insulator. An insulator I shown in the drawing includes a tubular portion Ia adapted to be loosely fit around a tooth T of a stator core S, which is formed by laminating electromagnetic steel plates, a flange Ib provided at one end of the tubular portion Ia, and fixed pieces Ic and Id that, when the insulator I is loosely fit around the tooth T (in the X2 direction), extend in the radial direction of the tooth T from two end sides of the flange Ib corresponding to the upper and lower end faces of the tooth T, and have claws Ic′ and Id′ for latching a coil C at the respective tip ends of the fixed pieces Ic and Id.
As described above, the coil C that is loosely fit around the tubular portion Ia (in the X1 direction) is latched by the two upper and lower fixed pieces Ic and Id, and then, the insulator I with the coil C is loosely fit around the tooth T. This is executed on all of the teeth T of the stator core SC.
When the insulator I with the coil C is loosely fit around each tooth T, an intermediate SM that is a precursor of the stator as a final product is produced as shown in FIG. 6A.
Next, as shown in FIG. 6B, the intermediate SM is placed in a die M and the die M is closed (FIG. 6B shows a state in which the die is closed), and then, resin is injected into an injection gate Ma provided in the die M (in the Y direction).
The resin is injected into regions around the teeth T, the insulators I, and the coils C. Then, after the resin has hardened, the components are removed from the die. Accordingly, a stator S is produced as shown in FIG. 7 in which the insulator and the coil disposed around each tooth T of the stator core SC are integrally sealed by a sealing resin body F.
In such a production method, when resin is injected into the die shown in FIG. 6B, the latched state of the coil C is maintained by the two upper and lower fixed pieces Ic and Id of the insulator I. Thus, movement of the coil C relative to the insulator I, which would otherwise occur due to the pressure of the injected resin, is suppressed. With respect to the suppression of the movement of the insulator I relative to the tooth T due to the pressure of the injected resin, movement of the insulator I is also suppressed as the resin is injected from the inner side of the insulator I (i.e., claw side of the fixed pieces) and the insulator I is thus pressed against the root side (i.e., yoke side) of the tooth T due to the pressure of the resin. As the insulator I is pressed against the root side of the tooth T (i.e., outer side of the stator core) as described above, it is possible to solve the problem of the performance deterioration of the stator resulting from an increase in copper loss that would be problematic if the coil C is disposed on the inner side (i.e., rotor side) of the stator core.
However, as the insulator I has the two fixed pieces Ic and Id at the top and the bottom thereof, there is a problem in that high labor and cost are required for producing the insulator I.
To address such a problem, Patent Document 1 discloses an insulator with a single fixed piece. A method for producing a stator that uses such an insulator (Embodiment 2 of the conventional production method) will be described with reference to FIGS. 8 and 9.
As shown in FIG. 8, an insulator IA includes a tubular portion Ia adapted to be loosely fit around each tooth T, a flange Ib provided at one end of the tubular portion Ia, and a fixed piece Ic that, when the insulator I is loosely fit around the tooth T (in the X2 direction), extends in the radial direction of the tooth T from one end side of the flange Ib corresponding to the upper end face of the tooth T, and has a claw Ic′ for latching a coil C at the tip end of the fixed piece Ic.
The coil C that is loosely fit around the tubular portion Ia (in the X1 direction) is latched only by the single upper fixed piece Ic, and then, the insulator IA with the coil C is loosely fit around the tooth T. This is executed on all teeth T of the stator core SC so that an intermediate SM′ shown in FIG. 9A is produced.
Next, as shown in FIG. 9B, the intermediate SM′ is placed in a die M, and resin is injected into an injection gate Ma (in the Y direction).
However, as shown in FIG. 9C, when the resin is injected, another problem can occur that a winding wire of the coil C on the side where the coil C is not directly latched by the fixed piece Ic may become loose (in the Z direction).